Excavator data acquisition and control system and process

ABSTRACT

A data acquisition system for acquiring geological information from a subsurface includes a geologic imaging system that is used to survey the subsurface of a site or route. A geologic characterization unit may also be employed to enhance the geologic imaging data obtained by the geologic imaging system. The acquired data are processed to provide detailed geologic information for the subsurface. In one embodiment, a memory stores geologic filter data including geologic profile data for numerous types of known geology. A processor, cooperating with the memory and data acquisition unit, uses the geologic filter data to remove content from the acquired geologic imaging data corresponding to known geology, thereby providing for immediate recognition of unknown and suspect subsurface characteristics. In another embodiment, the memory stores excavation difficulty data associated with known types of geology. The processor associates a reflected electromagnetic signal received by the geologic imaging system with the excavation difficulty data to produce estimated excavation difficulty data for the subsurface. The geologic imaging system may include a ground penetrating radar system having a plurality of antennas oriented in an orthogonal relationship to provide three-dimensional imaging of a subsurface.

This is a continuation of application Ser. No. 08/491,679, filed Jun.19, 1995, now U.S. Pat. No. 5,553,407, which application(s) areincorporated herein by reference.

The present invention relates generally to the field of data acquisitionand, more particularly, to a system and process for acquiring geologicaldata for a subsurface.

BACKGROUND OF THE INVENTION

Various types of excavators have been developed to excavate apredetermined site or route in accordance with a particular manner ofexcavation. One particular type of excavator, often referred to as atrack trencher, is typically utilized when excavating long continuoustrenches for purposes of installing and subsequently burying varioustypes of pipelines and utility conduits. A land developer or contractormay wish to excavate several miles or even hundreds of miles of terrainhaving varying types of unknown subsurface geology.

Generally, such a contractor will perform a limited survey of apredetermined excavation site in order to assess the nature of theterrain, and the size or length of the terrain to be excavated. One ormore core samples may be analyzed along a predetermined excavation routeto better assess the type of soil to be excavated. Based on varioustypes of qualitative and quantitative information, a contractor willgenerally prepare a cost budget that forecasts the financial resourcesneeded to complete the excavation project. A fixed cost bid is oftenpresented by such a contractor when bidding on an excavation contract.

It can be appreciated that insufficient, inaccurate, or misleadingsurvey information can dramatically impact the accuracy of a budget orbid associated with a particular excavation project. An initial survey,for example, may suggest that the subsurface geology for all or most ofa predetermined excavation route consists mostly of sand or loosegravel. The contractor's budget and bid will, accordingly, reflect thecosts associated with excavating relatively soft subsurface soil. Duringexcavation, however, it may instead be determined that a significantportion of the predetermined excavation route consists of relativelyhard soil, such a granite, for example. The additional costs associatedwith excavating the undetected hard soil are typically borne by thecontractor. It is generally appreciated in the excavation industry thatsuch unforeseen costs can compromise the financial viability of acontractor's business.

Various methods have been developed to analyze subsurface geology inorder to ascertain the type, nature, and structural attributes of theunderlying terrain. Ground penetrating radar and infrared thermographyare examples of two popular methods for detecting variations insubsurface geology. These and other non-destructive imaging analysistools, however, suffer from a number of deficiencies that currentlylimit their usefulness when excavating long, continuous trenches, orwhen excavating relatively large sites. Further, conventional subsurfaceanalysis tools typically only provide an image of the geology of aparticular subsurface, and do not provide information regarding thestructural or mechanical attributes of the underlying terrain which iscritical when attempting to determine the characteristics of the soil tobe excavated.

There is a need among developers and contractors who utilize excavationmachinery to minimize the difficulty of determining the characteristicsof subsurface geology at a predetermined excavation site. There exists afurther need to increase the production efficiency of an excavator byaccurately characterizing such subsurface geology. The present inventionfulfills these and other needs.

SUMMARY OF THE INVENTION

The present invention is directed to a data acquisition system andprocess for acquiring geological information from a subsurface. The dataacquisition system includes a geologic imaging system that is used tosurvey the subsurface of a site or route. A geologic characterizationunit may also be employed to enhance the geologic imaging data obtainedby the geologic imaging system. The acquired data are processed toprovide detailed geologic information for the subsurface.

In one embodiment, a memory stores geologic filter data includinggeologic profile data for numerous types of known geology. A processor,cooperating with the memory, uses the geologic filter data to removecontent from the acquired geologic imaging data corresponding to knowngeology, thereby providing for immediate recognition of unknown orsuspect subsurface characteristics.

In another embodiment, the memory stores excavation difficulty dataassociated with excavating through known types of geology. The processorassociates a reflected electromagnetic signal received by the geologicimaging system with the excavation difficulty data to produce estimatedexcavation difficulty data for the subsurface. The geologic imagingsystem may include a ground penetrating radar system having a pluralityof antennas oriented in an orthogonal relationship to providethree-dimensional imaging of a subsurface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of one embodiment of an excavator, termed a tracktrencher, including a ditcher chain trenching attachment;

FIG. 2 is a generalized system block diagram of a track trencherembodiment of an excavator;

FIG. 3 is an illustration of a main user interface for controlling atrack trencher excavator, for viewing acquired geological and positiondata, and for interfacing with various electronic and electromechanicalcomponents of the excavator;

FIG. 4 is a system block diagram of a main control unit (MCU) of a novelexcavator data acquisition and control system;

FIG. 5 is a system block diagram of a geologic data acquisition unit(GDAU) of a novel excavator data acquisition and control system;

FIG. 6 is plot of reflected source electromagnetic signals received by aground penetrating radar system using a conventional single-axis antennasystem;

FIG. 7 is a system block diagram of a geographic positioning unit (GPU)of a novel excavator data acquisition and control system;

FIG. 8 is a system block diagram of an excavator control unit (ECU) of anovel excavator data acquisition and control system;

FIG. 9 is a block diagram of various databases and software accessed andprocessed by the main control unit (MCU);

FIG. 10 is an illustration of a predetermined excavation site having aheterogenous subsurface geology;

FIG. 11 is an illustration of a survey profile in chart form obtainedfor a predetermined excavation route using a novel geologic dataacquisition unit (GDAU) and geologic positioning unit (GPU);

FIG. 12 is an illustration of an estimated excavation production profilein chart form corresponding to the survey profile chart of FIG. 11;

FIG. 13 is an illustration of a predetermined excavation site having aheterogenous subsurface geology and an unknown buried object;

FIG. 14 is an illustration of a conventional single-axis antenna systemtypically used with a ground penetrating radar system for providingtwo-dimensional subsurface geologic imaging;

FIG. 15 is an illustration of a novel antenna system including aplurality of antennas oriented in an orthogonal relationship for usewith a ground penetrating radar system to provide three-dimensionalsubsurface geologic imaging;

FIG. 16 is an illustration of a partial grid of city streets and anexcavator equipped with a novel excavator data acquisition and controlsystem employed to accurately map a predetermined excavation site; and

FIGS. 17-20 illustrate in flow diagram form generalized method steps foreffecting a novel excavator data acquisition and control process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The novel excavator data acquisition and control system and processprovides for a substantial enhancement in excavation efficiency andproject cost estimation by the acquisition and processing of geological,geophysical, and geographic position information for a particularexcavation site. The operation of an excavator is preferably optimizedby modifying excavator operating parameters based on acquired surveydata and input commands received from an operator of the excavator. Theaccuracy of estimating the resources and costs associated withexcavating a particular excavation site is significantly increased byproviding a computational analysis of the acquired survey data prior toinitiating excavation of the site, thereby substantially reducing acontractor's risk of misquoting the costs associated with a particularexcavation project due to a lack of accurate and detailed informationregarding the geology of the subject excavation site.

The advantages and features of a novel excavator data acquisition andcontrol system and process will generally be discussed with reference toone particular type of excavator, termed a track trencher. It is to beunderstood, however, that a track trencher represents only one of manyembodiments of an excavator that may be equipped with a novel excavatordata acquisition and control system as disclosed hereinbelow. As such,the advantages and features of the disclosed novel system and processare not limited to application in connection with a track trencher.

Referring now to the figures, and more particularly to FIG. 1, there isshown an illustration of one embodiment of an excavator well-suited forincorporating a novel data acquisition and control system. A tracktrencher excavator, shown in FIGS. 1 and 2, typically includes an engine36 coupled to a right track drive 32 and a left track drive 34 whichtogether comprise the tractor portion 45 of the track trencher 30. Anexcavation attachment 46, usually coupled to the front of the tractorportion 45, typically performs a specific type of excavating operation.

A ditcher chain 50, or other excavation attachment, is often employed todig trenches of varying width and depth at an appreciable rate. Theditcher chain 50 generally remains above the ground in a transportconfiguration 56 when maneuvering the trencher 30 around an excavationsite. During excavation, the ditcher chain 50 is lowered, penetrates theground, and excavates a trench at the desired depth and speed while in atrenching configuration 58. Another popular trenching attachment, termeda rock wheel in the art, may be controlled in a manner similar to thatof the ditcher chain 50. A track trencher 30 is well-suited forefficiently excavating a trench along a predetermined excavation routefor the purpose of installing various types of pipelines and utilityconduits.

In FIG. 3, there is illustrated a main user interface 101 of a tracktrencher 30. Propulsion and steering of a track trencher 30 whenoperating in a transport mode is generally controlled by manipulatingthe left and right track levers 64 and 66 which respectively controlactuation of the left and right track drives 34 and 32. Moving the righttrack lever 66 forward, for example, generally causes the right trackdrive 32 to operate in a forward direction and, depending on therelative velocity of the left track drive 34, steers the track trencher30 to move in either a left or right direction. Reversing the righttrack drive 32 is generally accomplished by pulling the right tracklever 66 backwards, thereby causing the right track drive 32 to operatein a reverse direction. Propulsion of the left track drive 34 isaccomplished in substantially the same manner as that previouslydescribed with regard to the right track drive 32. Thus, both propulsionand steering are generally controlled by the track levers 64 and 66 of atrack trencher 30. Alternatively, the main user interface 101 may beconfigured to provide for independent steering and propulsion of theleft and right track drives 34 and 32, respectively.

It is often desirable to maintain the engine 36 at a constant, optimumoutput level during excavation which, in turn, allows the attachment 46to operate at an optimum excavating output level. A prior art controlpanel typically includes a plurality of controls and switches, includinga speed range switch, RPM knob, steering trim knob, and propel trimknob, all of which must typically be adjusted during normal trenchingoperation to maintain the engine at the desired engine output level whenencountering variable attachment 46 loading, and to steer the tracktrencher 30 in a desired direction. Additionally, a pair of right andleft pump potentiometers typically require adjustment and readjustmentto equilibrate the operational characteristics of the left and rightpumps 38 and 40.

A significant disadvantage of a conventional track trencher controlpanel concerns a requirement that the operator must generally reactquickly to changes in engine 36 loading, typically by first determiningthe appropriate switch to adjust and then the degree of switchadjustment. Typically, minor propulsion modifications are made byadjusting the propel trim knob. Moderate changes to the propulsion levelof the track trencher 30 are generally effected by adjusting the RPMknob. A major modification to the propulsion level of the track trencher30 is typically accomplished by switching the speed range switch from ahigh setting to either a medium or low setting, and once again adjustingthe propel trim knob and RPM knob in order to avoid stalling out theengine 36.

The novel data acquisition and control system and process obviates therequirement of continuous manual adjustment and readjustment of aplurality of control switches, knobs, and levers. Instead, anintelligent excavation control unit (ECU) is employed to continuouslymonitor a network of sensors that transduce various excavator functionsinto electrical signals, and processes these and other electricalsignals to optimize the steering and excavating performance of theexcavator, with only minimal intervention by an excavator operator. Anenhanced user-interface communicates pertinent excavator performanceinformation, as well as geological and geographical position data, to anoperator preferably over a display, such as a liquid crystal display ora cathode ray tube display, for example. A keyboard and other levers andswitches are provided on the user-interface to communicate with the dataacquisition and control system, and control the operation of theexcavator.

DATA ACQUISITION AND CONTROL SYSTEM

Turning now to FIG. 4, there is illustrated a novel data acquisition andcontrol system shown in system block diagram form. In broad and generalterms, the system shown in FIG. 4 significantly enhances the operationof an excavator by the acquisition of geological, geophysical, andposition information regarding a particular excavation site, and byemploying this information to enhance excavation efficiency. Theacquisition of such pertinent excavation site data substantially reducesthe risk involved in estimating the cost and scheduling of a particularexcavation project. Real-time acquisition of geographical position dataprovides for precision mapping of an excavated area to accuratelyidentify the location and depth of, for example, buried pipelines andutility conduits installed at the excavation site. These and othersignificant advantages and features are provided by the novel excavatordata acquisition and control system and process as discussed in greaterdetail hereinbelow.

Referring to FIG. 4 in greater detail, the primary processing componentof the novel data acquisition and control system is a main control unit(MCU) 250, which preferably includes a central processing unit (CPU)264, Random-Access-Memory (RAM) 266, and non-volatile memory 286, suchas Electrically Erasable Programmable Read-Only-Memory (EEPROM). The MCU250 preferably includes appropriate input and output ports tocommunicate with a number of other sub-systems that acquire varioustypes of data, process such data, and interface with the control systemof an excavator to moderate and optimize the excavation process. A mainuser interface (MUI) 101 is preferably situated in proximity to anoperator seat mounted to the excavator, and provides a means forcommunicating with the main control unit 250. An excavator control unit(ECU) 255 communicates with the main control unit 250 and is responsiveto operator inputs received from the main user interface 101 tocooperatively control the operation of the excavator. A computer orprogrammable controller 182 is preferably incorporated as a component ofthe excavator control unit 255 to control and moderate excavatorfunction.

The movement and direction of an excavator is preferably monitored and,if desired, moderated by a geographic positioning unit (GPU) 254. Thegeographic positioning unit 254 preferably includes a mobile transpondermounted to the excavator and one or more reference transponders.Position reference signals produced by the reference transponders areprocessed by a CPU 270 of the geographic positioning unit 254 intogeographic position data, such as latitude, longitude, and elevationdata, and displacement data from one or more reference locations, forexample.

An important component of the novel data acquisition and control systemconcerns a geophysical data acquisition unit (GDAU) 256, which acquiresvarious types of geological and geophysical data for a particularexcavation site. In one embodiment, the geophysical data acquisitionunit 256 may be decoupled from the main control unit 250 to provide forinitial surveying of a predetermined excavation site. After performingthe initial survey, the data acquired by the geophysical dataacquisition unit 256 is preferably downloaded into the RAM 266 or EEPROM268 of the main control unit 250. Alternatively, the geophysical dataacquisition unit 256 is preferably coupled to the excavator and directlyto the main control unit 250 to provide real-time acquisition ofgeological, geophysical, and position data during excavation. In yetanother embodiment, initial surveying of an excavation site provides forthe acquisition of pertinent geological, geophysical, and position datawhich is downloaded to the main control unit 250 upon completion of theinitial survey. An onboard geophysical data acquisition unit 256, whichpreferably includes the components used in the initial survey, providesfor real-time data acquisition which may be used in conjunction with thedata acquired from the initial survey to optimize excavator productionperformance. The geophysical data acquisition unit 256 preferablyincludes a CPU 276, RAM 278, and EEPROM 280.

Among the various types of data acquired by the geophysical dataacquisition unit 256, data pertaining to the specific geology at theexcavation site, in addition to the physical characteristics of suchgeology, are of particular importance when optimizing the productionperformance of an excavator, and when estimating the cost and resourceallocation of a particular excavation project. A geologic imaging unit(GIU) 258 is preferably coupled to the geophysical data acquisition unit256 to provide information concerning the particular geology associatedwith an excavation site. Various geophysical characteristics associatedwith a particular geology at the excavation site are preferablydetermined by a geophysical characterization unit (GCU) 260. Anauxiliary user interface (AUI) 262 is preferably coupled to thegeophysical data acquisition unit 256 to provide local viewing ofacquired data and images, and to provide a means for an operator tocommunicate with the geophysical data acquisition unit 256. Theauxiliary user interface 262 is particularly useful in connection withan embodiment in which the geophysical data acquisition unit 256 isdecoupled from the main control unit 250 to perform an initial survey ofan excavation site. It is noted that RS-232 communication lines providesufficient bandwidth for effecting communication between the electronicunits and instruments of the novel data acquisition and control system.

GEOPHYSICAL DATA ACQUISITION UNIT (GDAU)

As shown in FIG. 5, the geophysical data acquisition unit 256 preferablyincludes a geologic imaging unit 258 and a geophysical characterizationunit 260. The geophysical characterization unit 260 preferably includesa number of geophysical instruments which provide a physicalcharacterization of the geology for a particular excavation site. Aseismic mapping module 286 includes an electronic device consisting ofmultiple geophysical pressure sensors. A network of these sensors arearranged in a specific orientation with respect to the excavator, andare situated so as to make direct contact with the ground. The networkof sensors measures ground pressure waves produced below the excavatorand in the trench walls produced by the excavator. Analysis of groundpressure waves received by the network of sensors provides a basis fordetermining the physical characteristics of the subsurface at theexcavation site. This data is preferably processed by the CPU 276 of thegeophysical data acquisition unit 256 or, alternatively, by the CPU 264of the main control unit 250.

A point load tester 288 may be employed to determine the geophysicalcharacteristics of the subsurface at the excavation site. The point loadtester 288 preferably employs a plurality conical bits for the loadingpoints which, in turn, are brought into contact with the ground to testthe degree to which a particular subsurface can resist a calibratedlevel of loading. The data acquired by the point load tester 288provides information corresponding to the geophysical mechanics of thesoil under test. This data may also be transmitted to the geophysicaldata acquisition unit 256 for storage in the RAM 278 or EEPROM 280.

The geophysical characterization unit 260 preferably includes a Schmidthammer 290, which is a geophysical instrument that measures the reboundhardness characteristics of a sampled subsurface geology. Othergeophysical instruments may also be employed to measure the relativeenergy absorption characteristics of a rock mass, abrasivity, rockvolume, rock quality, and other physical characteristics that togetherprovide information regarding the relative difficulty associated withexcavating a given geology. The data acquired by the Schmidt hammer 290is also preferably stored in the RAM 278 or EEPROM 280 of thegeophysical data acquisition unit 256.

The geologic imaging unit 258 preferably includes a ground penetratingradar system (GPRadar) 282 and an antenna system 284. The GPRadar system282 cooperates with the antenna system 284 to transmit sourceelectromagnetic signals into the subsurface of an excavation site. Thesource electromagnetic signals penetrate the subsurface and arereflected back to the antenna system 284. The reflected sourceelectromagnetic signals received by the antenna system 284 are amplifiedand conditioned by the GPRadar system 282. In one embodiment, analogreflected source electromagnetic signals processed by the GPRadar system282 are preferably digitized and quantized by a quantizer 281. Inanother embodiment, a digitizing GPRadar system 282 performsanalog-to-digital conversion of the reflected source electromagneticsignals. The digitized radar data acquired by the geologic imaging unit258 is preferably stored in RAM 278 or non-volatile EEPROM 280 memory inthe geophysical data acquisition unit 256.

Referring now to FIG. 6, there is illustrated a visual illustration oftypical geologic imaging data acquired from a GPRadar System 282employing a conventional single-axis antenna system 284. In FIG. 6,there is plotted GPRadar system 282 data acquired over a test sitehaving five different man-made hazards buried at a depth ofapproximately 1.3 meters in sandy soil with a water table located at adepth of approximately four to five meters. It is noted that the dataillustrated in FIG. 6 is representative of data typically obtainable byuse of a PulseEKKO 1000 system manufactured by Sensors and Software,Inc. using conventional single-axis 450 MHz center frequency antennas.Other GPRAdar systems 282 which may be suitable for this applicationinclude SIR System-2 and System-10A manufactured by Geophysical SurveySystems, Inc. and model 1000B STEPPED-FM Ground Penetrating Radarmanufactured by GeoRadar, Inc.

Each of the buried hazards illustrated in FIG. 6 has associated with ita characteristic hyperbolic time-position curve. The apex of thecharacteristic hyperbolic curve provides an indication of both theposition and the depth of a buried hazard. It can be seen from the graphof FIG. 6 that each of the buried hazards is located approximately 1.3meters below the ground surface, with each of the hazards beingseparated from adjacent hazards by a horizontal distance ofapproximately five meters. The GPRadar System 282 data illustrated inFIG. 6 represents geological imaging data acquired using a conventionalsingle-axis antenna system and, as such, only provides a two-dimensionalrepresentation of the subsurface being surveyed. As will be discussed ingreater detail hereinbelow, a novel antenna system 284 comprisingmultiple antennas arranged in an orthogonal orientation provides for anenhanced three-dimensional view of the subsurface geology associatedwith a particular excavation site.

GEOGRAPHIC POSITIONING UNIT (GPU)

Turning now to FIG. 7, there is illustrated in greater detail ageographic positioning unit 254 that provides geographic positioninformation regarding the position, movement, and direction of anexcavator over an excavation site. In one embodiment, the geographicpositioning unit 254 communicates with one or more external referencesignal sources to determine information regarding the position of anexcavator relative to one or more known reference locations. Therelative movement of an excavator over a specified excavation route ispreferably determined by the CPU 270 of the geographic positioning unit254, and stored as position data in RAM 272 or EEPROM 274.

In another embodiment, geographic position data for a predeterminedexcavation route is preferably acquired prior to excavating the route.This position data may be uploaded into a navigation controller 292which cooperates with the main control unit 250 and the excavatorcontrol unit 255 to provide autopilot-like control and maneuvering ofthe excavator over the predetermined excavation route. In yet anotherembodiment, position data acquired by the geographic positioning unit254 is preferably communicated to a route mapping database 294 whichstores the position data for a given excavation site, such as a grid ofcity streets or a golf course under which various utility,communication, plumbing, and other conduits are buried. The data storedin the route mapping database 294 may be subsequently used to produce asurvey map that accurately specifies the location and depth of variousutility conduits buried in a specified excavation area.

In one embodiment, a global positioning system (GPS) 296 is employed toprovide position data for the geographic positioning unit 254. Inaccordance with a U.S. Government project to deploy twenty-fourcommunication satellites in three sets of orbits, termed the GlobalPositioning System (GPS) or NAVSTAR, various signals transmitted fromone or more GPS satellites may be used indirectly for purposes ofdetermining positional displacement of an excavator relative to one ormore known reference locations. It is generally understood that the U.S.Government GPS satellite system provides for a reserved or protectedband and a civilian band. Generally, the protected band provides forhigh-precision positioning to an accuracy of approximately one to tenfeet. The protected band, however, is generally reserved exclusively formilitary and governmental surveillance purposes, and is modulated insuch a manner as to render it virtually useless for civilianapplications. The civilian band is modulated so as to significantlydecrease its usefulness in high-accuracy applications. In mostapplications, positional accuracies of approximately one hundred tothree hundred feet are typical using the civilian band.

The civilian GPS band, however, can be used indirectly in relativelyhigh-accuracy applications by using one or more civilian GPS signals incombination with one or more ground-based reference signal sources. Byemploying various known signal processing techniques, generally referredto as differential global positioning system (DGPS) signal processingtechniques, positional accuracies on the order of one foot or less areachievable. As shown in FIG. 7, the global positioning system 296utilizes a signal produced by at least one GPS satellite 302 incooperation with signals produced by at least two base transponders 304,although use of one base transponder 304 may be satisfactory in someapplications. Various known methods for exploiting differential globalpositioning signals using one or more base transponders 304, togetherwith a GPS satellite signal 302 and a mobile GPS receiver 303 mounted tothe excavator, may be employed to accurately resolve excavator movementrelative to base transponder 304 reference locations using a GPSsatellite signal source.

In another embodiment, a ground-based positioning system may be employedusing a range radar system 298. The range radar system 298 preferablyincludes a plurality of base radio frequency (RF) transponders 306 and amobile transponder 308 mounted to the excavator. The base transponders306 emit RF signals which are received by the mobile transponder 308.The mobile transponder 308 preferably includes a computer thatcalculates the range of the mobile transponder 308 relative to each ofthe base transponders 306 through various known radar techniques, andthen calculates its position relative to all base transponders 306. Theposition data acquired by the range radar system 298 is preferablystored in the RAM 272 or EEPROM 274 of the geographic positioning unit254.

An ultra-sonic positioning system 300, in another embodiment, may beemployed together with base transponders 310 and a mobile transponder312 mounted to the excavator. The base transponder 310 emits signalshaving a known clock timebase which are received by the mobiletransponder 312. The mobile transponder 312 preferably includes acomputer which calculates the range of the mobile transponder 312relative to each of the base transponders 310 by referencing the clockspeed of the source ultrasonic waves. The computer of the mobiletransponder 312 also calculates the position of the excavator relativeto all of the base transponders 310. It is to be understood that variousother known ground-based and satellite-based positioning systems may beemployed to accurately determine excavator movement along apredetermined excavation route.

EXCAVATOR CONTROL UNIT (ECU)

Referring now to FIG. 8, there is illustrated a system block diagram ofan excavator control unit (ECU) 255 which communicates with the maincontrol unit (MCU) 250 to coordinate the operation of an excavator. Inaccordance with an embodiment of the track trencher excavator 30illustrated in FIGS. 1 and 2, the left track drive 34 typicallycomprises a left track pump 38 coupled to a left track motor 42, and theright track drive 32 typically comprises a right track pump 40 coupledto a right track motor 44. Left and right track motor sensors 198 and192 are preferably coupled to the left and right track motors 42 and 44,respectively. The left and right track pumps 38 and 40, deriving powerfrom the engine 36, preferably regulate oil flow to the left and righttrack motors 42 and 44 which, in turn, provide propulsion for the leftand right track drives 34 and 32. The excavation attachment 46preferably comprises an attachment motor 48 and an attachment control98, with the attachment 46 preferably deriving power from the engine 36.A sensor 186 is preferably coupled to the attachment motor 46. Actuationof the left track motor 42, right track motor 44, and attachment motor48 is monitored by sensors 198, 192, and 186 respectively. The outputsignals produced by the sensors 198, 192, and 186 are communicated tothe computer 182.

In response to steering and propel control signals respectively producedby the steering control 92 and propel control 90, the computer 182communicates control signals, typically in the form of control current,to the left and right track pumps 38 and 40 which, in turn, regulate thespeed at which the left and right track motors 42 and 44 operate. Theleft and right track motor sensors 198 and 192 communicate track motorsense signals to the computer 182 indicative of the actual speed of theleft and right track motors 42 and 44. Similarly, an engine sensor 208,coupled to the engine 36, provides an engine sense signal to thecomputer 182, thus completing a closed-loop control system for thetractor drive portion 45 of a track trencher 30. Those skilled in theart will recognize that various known computer configurations willprovide a suitable platform for effectuating propulsion and steeringchanges of a track trencher 30 in response to the propel and steeringsignals produced by the propel and steering controls 90 and 92.

The excavation attachment 46 portion of a track trencher 30 includes anattachment motor 48, attachment control 98, and at least one attachmentsensor 186. The attachment motor 48 preferably responds to instructionscommunicated to the attachment control 98 from the computer 182. Theactual output of the attachment motor 48 is monitored by the attachmentsensor 186, which produces an attachment sense signal received by thecomputer 182.

In one embodiment, the left and right track motor sensors 198 and 192are of a type generally referred to in the art as magnetic pulsepickups, or PPUs. The PPUs 198 and 192 transduce track motor rotationinto a continuous series of pulse signals, wherein the pulse trainpreferably represents the frequency of track motor rotation as measuredin revolutions-per-minute. When a transport mode of travel is selected,the propel control 90 preferably produces a transport propel controlsignal which is representative of a target velocity for the left andright track motors 42 and 44, typically measured inrevolutions-per-minute. Conversion of the transport propel signal into atarget track motor velocity may be accomplished by the propel control 90itself or, preferably, by the computer 182. The computer 182 typicallycompares the left and right track motor sense signals respectivelyproduced by the left and right PPU sensors 198 and 192 to the targettrack motor propulsion level represented by the transport propel signal.The computer 182 communicates the appropriate pump control signals tothe left and right track pumps 38 and 40 in response to the outcome ofthe comparison to compensate for any deviation between the actual andtarget track motor propulsion levels.

A display 73 is coupled to the computer 182 or, alternatively, to themain Control unit 250, and preferably communicates messages indicativeof operating status, diagnostic, calibration, fault, safety, and otherrelated information to an operator. The display 73 provides quick,accurate, and easy-to-understand information to an operator by virtue ofthe interpretive power of the computer 182 which acquires and processesdata from a plurality of track trencher sensors, and various geologicaland geophysical instruments. Geologic imaging data and relatedgeophysical information, for example, is visually displayed on thedisplay 73. Further, information regarding the position of the excavatoras it traverses along a predetermined excavation route, as well assignal quality information received from the geographic positioning unit254, is displayed on the display 73. A keyboard 75 is also provided onthe main user interface 101 to permit an operator to communicate withthe excavator control unit 255 and the main control unit 250.

MAIN CONTROL UNIT (MCU)

Turning now to FIG. 9, there is illustrated a block diagram of variousdatabases and software that are utilized by the main control unit (MCU)250 when accessing and processing geological, geophysical, position, andoperational data associated with surveying and excavating a selectedexcavation site. The data acquired by the geophysic data acquisitionunit 256, for example, is preferably stored in a database 326, whichincludes a GPRadar database 328, a geologic filter database 330, and ageophysics database 332. The GPRadar system 282 data, as previouslydiscussed, is preferably digitized and stored in the GPRadar database328 in a suitable digital format appropriate for correlation to datastored in other system databases. A geologic filter database 330, aswill be discussed in greater detail hereinbelow, includes filtering dataproduced by correlating GPRadar data to corresponding excavatorproduction data stored in the excavation performance database 324.Correlation and optimization software 320 performs the correlation ofGPRadar data to actual excavator production data to develop an array ofadjustable geologic digital filters that can be effectively overlaidwith real-time acquired geologic image data to exclude or "filter out"verified geology data, thus leaving unverified images representative ofone or more buried hazards. By way of further illustration, a particulartype of soil produces a characteristic return radar image which can becorrelated with excavator production data acquired by the excavatorcontrol unit 255. Excavating through granite, for example, produces acharacteristic return radar image that can be correlated to variousexcavator operation parameters, such as excavation attachment motor 48speed, engine 36 loading, and left or right track motor 42 and 44velocity changes.

An "excavation difficulty" parameter or set of parameters are preferablycomputed based on the excavator operating parameters. The "excavationdifficulty" parameters are then associated with the characteristicreflected radar image data corresponding to a particular geology, suchas granite, for example. An array of "excavation difficulty" filterparameters and associated reflected radar image data values arepreferably developed for a wide range of soil and rock, and stored inthe geologic filter database 330.

An excavation statistics database 316 preferably receives data filesfrom the correlation and optimization software 320 and compilesstatistical data to reflect actual excavator production performancerelative to specific geology, maintenance, and equipment variables. Inone embodiment, GPRadar data and geophysical data is acquired by thegeophysic data acquisition unit 256 during an initial survey of apredetermined excavation route. This data is preferably uploaded to theexcavation statistics database 316 prior to excavating the predeterminedroute. The data stored in the excavation statistics database 316 can beviewed as a production estimate in the sample geology based on pastexcavator production performance.

The main control unit 250 also executes ECU control software 318 whichreceives data files from the correlation and optimization software 320and input commands received from the main user interface 101. The ECUcontrol software 318 compiles a current operation standard for operatingthe excavator over the course of the predetermined excavation route. Ifinput data received from the main user interface 101 causes amodification in the operation standard, the ECU control software 318computes modified excavator operational instructions which aretransmitted to the main control unit 250 and the excavator control unit255 which, in turn, modifies the operation of the excavator in responseto the modified operation standard.

A maintenance log memory 314 preferably includes non-volatile memory forstoring various types of excavator maintenance information. An elapsedtime indicator is preferably included in the maintenance log memory 314which indicates the total elapsed operating time of the excavator. Atpredefined operating time values, which are preferably stored in themaintenance log memory 314, the excavator operator is prompted by themain user interface 101 that scheduled service is required. Verificationscheduled service, the type of service, the date of service, and otherrelated information is preferably input through the main user interface101 for permanent storage in the maintenance log memory 314. In oneembodiment, the maintenance log memory 314 preferably includes a tableof factory designated operational values and ranges of operationalvalues associated with nominal excavator operation. Associated with eachof the operational values and ranges of values is a status counter whichis incremented upon each occurrence of excavator operation outside ofthe prescribed values or range of values. The status counter informationis useful in assessing the degree to which an excavator has beenoperated outside factory specified operational ranges, which isparticularly useful when determining the appropriateness of warrantyrepair work.

GEOLOGIC SURVEYING AND IMAGING

In general operation, as shown in FIG. 10, a predetermined excavationroute is preferably initially surveyed using the geographic positioningunit 254 and the geophysic data acquisition unit 256. In one embodiment,the geographic positioning unit 254 and geophysic data acquisition unit256 are positioned in a transport cart 340 which is pulled along thepredetermined excavation route by a vehicle 342. In the illustrativeexample shown in FIG. 10, the excavation route is a county road underwhich a utility conduit is to be installed. As the transport cart 340 ispulled along the roadway 344, data received from the geologic imagingunit 258 is acquired for the purpose of determining the soil propertiesof the subsurface below the roadway 344. Concurrently, geographicposition data is acquired by the geographic positioning unit 254 as thevehicle 342 and transport cart 340 traverse the roadway 344. As such,specific geologic data obtained from the geologic imaging unit 258 maybe correlated to specific geographic locations along the roadway 344.

The geologic imaging unit 258 preferably includes a GPRadar system 282which is typically calibrated to penetrate to a pre-established depthassociated with a desired depth of excavation. Depending on thepredetermined excavation depth, various types of soil and rock may beencountered along the predetermined excavation route. As shown in FIG.10, a layer of road fill 346, which lies immediately below the roadway344, has associated with it a characteristic geologic profile GP₁ and acorresponding geologic filter profile GF₁ which, as previouslydiscussed, represents a correlation between excavation productionperformance data to reflected radar image data for a particular soiltype. As the transport cart 340 traverses the roadway 344, various typesof soil and subsurface structures are detected, such as a sand layer354, gravel 352, bedrock 350, and native soil 348, each of which has acorresponding characteristic geologic profile and geologic filterprofile.

Upon completion of the initial survey, the data acquired and stored inthe geophysic data acquisition unit 256 and geographic positioning unit254 is preferably downloaded to a separate personal computer (PC) 252.The PC 252 preferably includes excavation statistics software and anassociated database 316 to correlate the acquired survey data withhistorical excavator production performance data to produce anestimation as to expected excavator performance over the ,surveyedroute. The performance estimates may further be used as a basis forcomputing the time and cost involved in excavating a particular areabased on actual geological data and historical production performancedata.

After completion of the initial survey, the geophysic data acquisitionunit 256 is preferably coupled to the main control unit 250 on theexcavator prior to initiating excavation along the surveyed route.During excavation, as previously discussed, the various databasescontaining geological, geophysical, position, and excavator operatingperformance data are processed by the main control unit 250. The maincontrol unit 250, in cooperation with the excavator control unit 255,adjusts the operation of the excavator as it traverses and excavatesalong the surveyed route to optimize excavation.

Referring now to FIG. 11, there is illustrated an example of a surveyprofile obtained by transporting the geophysic data acquisition unit 256and geographic positioning unit 254 along a predetermined excavationroute. It is noted that in this illustrative example, the length of theexcavation route is defined as the distance between Location L₀ andLocation L₅. A corresponding estimated excavation production profile forthe predetermined excavation route is shown in FIG. 12.

Referring to FIG. 11 in greater detail, distinct changes in subsurfacegeological characteristics can be observed at locations L₁, L₂, L₃, andL₄, which are associated with corresponding changes in the "excavationdifficulty" parameter plotted along the Y-axis of the survey profilechart. Between locations L₀ and L₁, for example, the geologic profileGP₁ 362 of the subsurface has associated with it a correspondingexcavation difficulty parameter of D₁. The geologic imaging data at L₁indicates a transition in the subsurface geology to soil having ageologic profile of GP₂ 364 and a corresponding excavation difficultyparameter of D₂, thus indicating a transition to relatively softer soil.

The estimated excavation production profile data shown in FIG. 12indicates a corresponding transition from an initial production profilePP₁ 372 to another production profile PP₂ 374 at location L₁. It isnoted that the rate of excavation is plotted along the Y-axis of theexcavation production profile chart. Based on the survey profile datafor the subsurface geological characteristics between locations L₀ andL₂, it can be seen that an initial excavation rate R₁ is estimated forthe portion of the predetermined excavation route between locations L₀and L₁, and an increased excavation rate of R₂ between excavation routelocations L₁ and L₂ due to the lower excavation difficulty parameter D₂associated with geologic profile GP₂ 364. It can be seen that a similarrelationship exists between a particular excavation difficulty parameterand its corresponding estimated excavation rate parameter.

In general, excavation difficulty parameters of increasing magnitude areassociated with corresponding excavation rate parameters of decreasingmagnitude. This generalized inverse relationship reflects the practicalresult that excavating relatively hard soil, such as granite, results ina relatively low excavation rate, while excavating relatively soft soil,such as sand, results in relatively high excavation rates. It is notedthat associated with each particular geologic profile (GP_(X)) andproduction profile (PP_(X)), there exists a corresponding excavationtime, such as excavation time T₁ associated with geologic profile GP₁362 and production profile PP₁ 372. As such, a total estimatedexcavation time for a particular predetermined excavation route can beobtained by summing each of the individual excavation time parameters T₁through T_(N).

The survey profile data of FIG. 11 associated with geologic profile GP₄368 between excavation route locations L₃ and L₄ indicates adiscontinuity at this location. The excavation production profile dataof FIG. 12 corresponding to this portion of the predetermined excavationroute indicates a corresponding discontinuity in the excavation rateestimation which is shown diverging toward zero. The data for thisportion of the predetermined excavation route indicates the existence ofextremely tough soil or, more likely, a man-made hazard, such as aconcrete or steel pipeline, for example. Further investigation andsurveying of the specific area may be warranted, which may requireremoval of the hazard or modification to the predetermined excavationroute.

A more realistic geologic profile for a particular length of thepredetermined excavation route is illustrated as geologic profile GP₅370 shown between excavation route locations L₄ and L₅. The excavationdifficulty parameter for this geologic profile results in an averagedparameter of D₅. Accordingly, an averaged excavation rate of R₅ may beappropriate when excavating this portion of the predetermined route.Alternatively, the excavation rate associated with the productionprofile PP₅ 380 may be moderated by the excavator control unit 255 tooptimize the excavation rate based on such fluctuations in excavationdifficulty. It is understood that the ability of an excavator to respondto such fluctuations in excavation rate is generally limited by variousmechanical and operational limitations.

Turning now to FIG. 13, there is illustrated a heterogeneous compositionof differing soil types over a predetermined excavation route having apredefined distance of L_(S). The soil in region 1, for example, has ageologic profile of GP₁ and a corresponding geologic filter profile ofGF₁. Each of the other soil types illustrated in FIG. 13 has acorresponding geologic profile and geologic filter profile value. It isassumed that the geologic filter database 330 contains geologic filterdata for each of the regions 1, 2, 3 and 4 illustrated in FIG. 13. Asignificant advantage of the novel hazard detection process performed bythe geophysic data acquisition unit 256 concerns the ability to quicklydetect the existence of an unknown buried structure 401. The correlationand optimization software 320 executed by the main control unit 250preferably filters out known geology using a corresponding knowngeologic filter profile to exclude the known or verified geology datafrom data associated with a survey scan image. Filtering out orexcluding the known or verified geology data results in imaging onlyunverified buried structures 401. By excluding known geological datafrom geologic imaging survey scan data, unknown or suspect buriedstructures are clearly recognizable.

Referring now to FIG. 14, there is illustrated a conventional antennaconfiguration for use with a ground penetrating radar system. Generally,a single-axis antenna, such as the one illustrated as antenna-A 382oriented along the Z-axis, is employed to perform multiple survey passes384 when attempting to locate a potential buried hazard 386. Generally,a ground penetrating radar system has a time measurement capabilitywhich allows measuring of the time for a signal to travel from thetransmitter, bounce off a target, and return to the receiver. This timefunction can be calibrated to the velocity of a specific subsurfacecondition in order to measure distance to a subsurface object orhorizon. Calculations can be used to convert this time value to adistance measurement that represents the depth of the target based uponfield determined values for characteristic soil properties, such adielectric and wave velocity through a particular soil type. Asimplified technique that can be used when calibrating the depthmeasurement capabilities of a particular ground penetrating radar systeminvolves coring a sample target, measuring its depth, and relating it tothe number of nanoseconds it takes a wave to propagate.

After the time function capability of the ground penetrating radarsystem provides an operator with depth information, the radar system ismoved laterally in a horizontal (X) direction, thus allowing for theconstruction of a two-dimensional profile of a subsurface. By performingmultiple survey passes in a series of parallel lines 384 over aparticular site, a buried hazard 386 may be located. It can beappreciated, however, that the two-dimensional imaging capability of aconventional antenna configuration 382 can result in missing a buriedhazard 386, particularly when the hazard 386 is parallel to thedirection of a survey pass 384.

A significant advantage of a novel geologic imaging antennaconfiguration 284 provides for three-dimensional imaging of a subsurfaceas shown in FIG. 15. A pair of antennas, antenna-A 388 and antenna-B390, are preferably employed in an orthogonal configuration to providefor three-dimensional imaging of a buried hazard 386. It is noted thatthe characteristic hyperbolic time-position data distribution, as shownin two-dimensional form in FIG. 6 by use of a conventional single-axisantenna, may instead be plotted as a three-dimensional hyperbolic shapethat provides width, length, and breadth dimensions of a detected buriedhazard 386. It is further noted that a buried hazard 386, such as adrainage pipeline, which runs parallel to the survey path 392 willimmediately be detected by the three-dimensional imaging GPRadar system282. Respective pairs of orthogonally oriented transmitting andreceiving antennas are preferably employed in the antenna system 284 ofthe geological imaging unit 258.

EXCAVATION SITE MAPPING

Turning now to FIG. 16, there is illustrated an excavator 410 performingan excavation operation along a city street 420 of a city street grid422. An important advantage of the novel geographic positioning unit 254of the excavator 410 concerns the ability to accurately navigate along apredetermined excavation route, such as a city street 420, and toaccurately map the excavation route in a route mapping database 294coupled to the geographic positioning unit 254. It may be desirable toinitially survey a city street grid 422 for purposes of accuratelyestablishing an excavation route for each of the applicable city streets420 comprising the city street grid 422, for example. This data ispreferably loaded into the navigation controller 292 of the geographicpositioning unit 254.

As the excavator 410 progresses along the excavation route defined foreach of the city streets 420, actual position data is acquired by thegeographic positioning unit 254 and stored in the route mapping database294. Any deviation from the predetermined excavation route stored in thenavigation controller 292 is accurately recorded in the route mappingdatabase 294. Upon completion of an excavation effort, the data storedin the route mapping database 294 may be downloaded to a PC 252 toconstruct an "as built" excavation map of the city street grid 422.

Accordingly, an accurate survey map of utility or other conduitsinstalled along the excavation route may be constructed from the routemapping data and subsequently referenced by workers desiring to gainaccess to, or avoid, the buried conduits. It is to be understood thatexcavating one or more city streets for the purpose of installingutility conduits as shown in FIG. 16 is provided for illustrativepurposes, and does not represent a limitation on the application of thegeographic positioning and route mapping capability of the novelexcavator data acquisition and control system.

Still referring to FIG. 16, accurate navigation and mapping of aprescribed excavation route may be accomplished by a global positioningsystem 296, range radar system 298 or ultrasonic positioning system 300,as discussed previously with respect to FIG. 7. An excavator dataacquisition and control system utilizing a GPS 296 configurationpreferably includes first and second base transponders 404 and 408together with one or more GPS signals received from a correspondingnumber of GPS satellites 302. A mobile transponder 402, preferablymounted to the excavator 410, is provided for receiving the GPSsatellite signal 412 and base transponder signals 414 and 418respectively transmitted from the base transponders 404 and 408. Aspreviously discussed, a modified form of differential GPS positioningtechniques may be employed to enhance positioning accuracy to one footor less.

In another embodiment, a ground-base range radar system 298 includesthree base transponders 404, 408, and 406 and a mobile transponder 402mounted to the excavator 410. It is noted that a third ground-basedtransponder 406 may be provided as a backup transponder for a systememploying a GPS satellite signal 412 in cases where a GPS satellitesignal 412 transmission is temporarily terminated. Position data ispreferably processed and stored by the geographic positioning unit 254using the three reference signals 414, 416, and 418 received from thethree ground-based radar transponders 404, 406, and 408. An embodimentemploying an ultrasonic positioning system 300 would similarly employthree base transponders, 404, 406, and 408 together with a mobiletransponder 402 mounted to the excavator 410.

EXCAVATOR DATA ACQUISITION AND CONTROL PROCESS

Turning now to FIGS. 17-20, there is illustrated in flowchart formgeneralized process steps associated with the novel excavator dataacquisition and control system and process. Initially, as shown in FIG.17, a number of ground-based transponders are positioned at appropriatelocations along a predetermined excavation route at step 500. Thegeophysic data acquisition unit 256 and geographic positioning unit 254are then situated at an initial location L₀ of the excavation route atstep 502. The geologic imaging unit 258, geophysical characterizationunit 260, and geographic positioning unit 254 are then initialized orcalibrated at step 504. After initialization, the geophysic dataacquisition unit 256 and geographic positioning unit 254 are transportedalong the excavation route, during which GPRadar, position, andgeophysical data is acquired at steps 506, 508, and 510. The dataacquired by the GPRadar system 282 is preferably digitized and quantizedat step 512. Data acquisition continues at step 516 until the end of theexcavation route is reached, as at step 518. The acquired data is thenpreferably downloaded to a PC 252 or directly to the main control unit250.

At step 530, shown in FIG. 18, excavation statistical software ispreferably executed on the data acquired during the excavation routesurvey. At step 532, historical excavator production data is transferredfrom the excavation statistics database 316 to the PC 252. The dataacquired during the survey is also loaded into the PC at step 534. Theexcavation statistical software then performs a correlation between theacquired GPRadar data and the historical excavator production data step536.

In one embodiment, correlation between GPRadar data and historicalproduction data is accomplished by use of various known matrixmanipulation techniques. A historical production data matrix ispreferably produced at step 538 by correlating geologic image data(ID_(X)) with corresponding excavator production data (PD_(X)). Acorrelation value (CV_(XX)) is produced corresponding to each pair ofgeologic image data and production data parameters. The correlationvalue CV₂₂, for example, is a correlation value associated with astatistical correlation between geologic image data parameter ID₂ andexcavator production data parameter PD₂. Associated with each geologicimage data parameter is an associated time parameter and locationparameter, such as T₁ and L₁ associated with geologic image dataparameter ID₁. It can be seen that correlation values associated with aplurality of geologic image data and production data parameter pairs canbe produced for time and position increments along a predeterminedexcavation route.

At step 540, actual geologic image data is acquired over the excavationroute and preferably processed as a matrix of discrete geologic imagedata for corresponding discrete time and location distance increments.At step 542, the matrices produced at steps 538 and 540 are manipulatedto produce a correlation matrix in which an estimated or projectedproduction data parameter (PD_(XX)) is associated with a pair ofcorresponding actual geologic image data (ID_(X)) and correlation value(CV_(X)) parameter pairs. For example, an estimated production dataparameter PD₃ is associated with actual geologic image data parameterID₃ and correlation value parameter CV₃. It is noted that each of theestimated production data parameters is associated with a correspondingtime and distance location increment.

The estimated production performance parameters for a particularexcavation route are computed at step 550 as shown in FIG. 19. The totalestimated time (ET_(T)) to excavate the entire excavation route can beestimated by summing the discrete time increments T₁ through T_(N). Theoperational costs associated with excavating the predeterminedexcavation route can be determined by summing the operational costsassociated with each of the discrete portions along the route. Theestimated labor costs (LC_(T)) can be estimated by multiplying the totalestimated excavation time (ET_(T)) by the total man hour cost per hour.An estimation of the grand total of costs (GT_(E)) can be determined bysumming all of the production costs and labor costs associated withexcavating the entire route.

At step 552, the estimated excavator operation parameters are computed.For the portion of the excavation route defined between referencelocation L₀ and L₁, for example, the estimated production data mayindicate an optimal left track velocity (V_(L)) of 125 feet per minute(FPM) and a right track velocity (V_(R)) of 125 FPM. Further, theestimated production data may suggest an optimal excavation attachmentspeed of approximately 110 RPM and a target engine speed of 2,250 RPM.It is noted that the left and right track velocities V_(L) and V_(R) of125 FPM, respectively, represents straight tracking by the excavatoralong the excavation route.

It can be seen that along the excavation route defined between locationL₁ and L₂, it is indicated that the excavator is steering in a rightdirection since the left track velocity V_(L) of 230 FPM is greater thanthe right track velocity V_(R) of 150 FPM. Also, it is indicated thatthe excavating attachment speed is increasing to 130 RPM, and that thetarget engine speed is increasing to 2,400 RPM, thus indicating thepresence of relatively softer soil within the region defined betweenlocations L₁ and L₂. Along the excavation route defined betweenlocations L₂ and L₃, it is indicated that the excavator is againtracking in a straight direction and at a relatively slow velocity of 60FPM, thus indicating the presence of relatively hard subsurface soil. Acorresponding slower excavating attachment speed of 100 RPM and lowertarget engine speed of 2,100 RPM are indicated due to the slowerexcavator velocity.

At step 560, as shown in FIG. 20, the estimated excavation operatingparameters produced at step 552 are loaded into the main control unit250. Excavation is initiated beginning at reference location L₀ at step562. At step 564, the main control unit 250 monitors the excavatoroperational parameters, and out-of-range conditions are recorded in themaintenance log memory Actual production performance parameters areacquired by the excavator control unit 255, at step 568, and transferredto the main control unit 250. Any inputs received from the main userinterface 101 are also transferred to the main control unit at step 570.If the actual production performance parameters received from theexcavator control unit 255 differ by a predetermined amount from theestimated excavation operation parameters, as tested at step 572, themain control unit 250 optimizes the estimated parameters at step 574,and transmits the optimized parameters to the excavator control unit 255to effect the necessary changes to excavator operation at step 576.Excavation continues at step 578 until the end location of thepredetermined excavation route is reached at step 580, after which theexcavation operation is terminated, as at step 582.

It will, of course, be understood that various modifications andadditions can be made to the preferred embodiments discussed hereinabovewithout departing from the scope or spirit of the present invention.Accordingly, the scope of the present invention should not be limited bythe particular embodiments discussed above, but should be defined onlyby the claims set forth below and equivalents of the disclosedembodiments.

What is claimed is:
 1. A data acquisition system for acquiringgeological information from a subsurface, comprising:a data acquisitionunit to acquire geological information from the subsurface, the dataacquisition unit including a signal processing unit to transmit an earthpenetrating source signal into the subsurface and to receive a reflectedsignal from the subsurface; a memory to store geologic filter datarepresentative of known subsurface geology; and a processor coupled tothe memory and the data acquisition unit that filters content of thereflected signal corresponding to the known subsurface geology using thegeologic filter data, the filtered reflected signal indicating apresence of a subsurface characteristic other than a characteristicassociated with the known subsurface geology.
 2. The system as claimedin claim 1, wherein the signal processing unit comprises a groundpenetrating radar unit.
 3. The system as claimed in claim 1, furthercomprising a display coupled to the processor to display an imagerepresentative of the filtered reflected signal.
 4. The system asclaimed in claim 1, wherein the signal processing unit is coupled to twoantennas orientated in an orthogonal relationship to transmit the earthpenetrating source signal into the subsurface and to receive thereflected signal from the subsurface.
 5. The system as claimed in claim4, further comprising a display coupled to the data acquisition unit todisplay a three-dimensional image of the subsurface.
 6. The system asclaimed in claim 1, further comprising a geographic positioning unit todetermine a location of the subsurface subjected to the earthpenetrating source signal.
 7. The system as claimed in claim 1, furthercomprising a geology characterization device to determine physicalcharacteristics of the subsurface.
 8. A data acquisition system foracquiring geological information at a site, comprising:a groundpenetrating radar unit to transmit a source electromagnetic signal intoa subsurface at the site and to receive a reflected electromagneticsignal from the subsurface; a memory to store excavation difficulty dataassociated with known types of geology and to store reflected signaldata corresponding to the reflected electromagnetic signal; and aprocessor coupled to the memory and the ground penetrating radar unitthat associates the reflected signal data with the excavation difficultydata to produce estimated excavation difficulty data for the subsurfaceat the site.
 9. The system as claimed in claim 8, further comprising adisplay coupled to the ground penetrating radar unit to display imagesof the subsurface using one of the reflected electromagnetic signal andthe reflected signal data.
 10. A system as claimed in claim 8, whereinthe ground penetrating radar unit is coupled to two antennas orientatedin an orthogonal relationship to transmit the source electromagneticsignal into the subsurface and to receive the reflected electromagneticsignal from the subsurface.
 11. A system as claimed in claim 10, furthercomprising a display coupled to one of the ground penetrating radar-unitand the processor to display a three-dimensional image of the subsurfaceusing one of the reflected electromagnetic signal and the reflectedsignal data.
 12. The system as claimed in claim 8, further comprising ageographic positioning unit to determine a location of the subsurfacesubjected to the source electromagnetic signal.
 13. The system asclaimed in claim 12, wherein the geographic positioning unit comprises aplurality of ground-based transponders and a Global Positioning Systemtransponder proximate the ground penetrating radar unit.
 14. The systemas claimed in claim 12, wherein the geographic positioning unitcomprises a plurality of radar transponders and a radar transponderproximate the ground penetrating radar unit.
 15. The system as claimedin claim 12, wherein the geographic positioning unit comprises aplurality of ultra-sonic radar transponders and an ultra-sonictransponder proximate the ground penetrating radar unit.
 16. The systemas claimed in claim 8, further comprising a geology characterizationdevice coupled to the processor, the geology characterization deviceincluding any one of a Schmidt hammer, a point load tester, and aseismic sensor.
 17. A method of characterizing a subsurface, includingthe steps of:acquiring geological imaging data for the subsurface;providing geologic filter data associated with known types of subsurfacegeology; and removing content of the geological imaging datacorresponding to the known types of subsurface geology using thegeologic filter data to produce filtered geologic imaging datarepresentative of a characteristic of the subsurface other than acharacteristic associated with the known types of subsurface geology.18. The method as claimed in claim 17, including the further step ofdisplaying an image of the subsurface using the filtered geologicimaging data.
 19. A method of characterizing a subsurface, including thesteps of:acquiring geologic imaging data for the subsurface; providingexcavation difficulty data associated with known types of geology; andassociating the geologic imaging data for the subsurface with theexcavation difficulty data to produce estimated excavation difficultydata for the subsurface.
 20. The method as claimed in claim 19,including the further step of displaying an image of the subsurfaceusing the geologic imaging data.